On the Strain-Hardening Behavior and Twin-Induced Grain Refinement of CP-Ti Under Ambient Temperature Compression

Abstract

In this paper, a systematic investigation on the twin-induced grain fragmentation of commercially pure Titanium was carried out under quasi-static uniaxial compression test at ambient temperature. The compression tests were interrupted at various strain levels in order to examine the progressive evolution of the microstructure and texture. The detailed microstructural analysis was performed using the electron backscattered diffraction technique. The microstructural features indicated the presence of \( \{ 10\bar{1}2\} \) extension twins (ET), \( \{ 11\bar{2}2\} \) contraction twins (CT) and their interactions. The strain-hardening behavior of the material corroborates with the microstructural evidences. The strain-hardening rate and its derivative clearly distinguish the regions of slip- and twin-dominating zones with the increasing strain. The deformation texture substantiates that along with the twins, dislocation slips were active. The slip-based deformation finally deviates the twin boundaries from its special character at medium-to-high strains. At low strains, ET originate in texturally soft grains. These twin domains are comparatively texturally harder. They interact to form ET–ET with ~ 56.8 deg about \( \langle 10\bar{1}0 \rangle \), with twin lamellar structure and consumes the entire parent grain with further deformation by twin expansion. CT develop on texturally hard grains with subsequent strains and were texturally softer. CT–CT, ET–CT-type twin interactions, and CT–ET double twins with ~ 77, ~ 87, and ~ 44.5 deg about \(\langle 10\bar{1}0 \rangle \), \(\langle 4\bar{2}\bar{2}1 \rangle \) and \(\langle 5\bar{1}\bar{4}0 \rangle \) axes, respectively, were observed. The microstructural changes corresponding to twin-boundary migration, interaction, and grain refinement are discussed on the basis of grain orientation spread and grain reference orientation deviation.

Notes

Acknowledgments

The authors would like to acknowledge the financial grants provided by the ISIRD, SRIC, IIT Kharagpur, India and Science; and the Engineering Research Board (Ref. No. ECR/2016/000125), Department of Science and Technology, Government of India to carry out the experiments. The authors sincerely acknowledge the prolific and helpful discussions they had with Professor Laszlo Toth and Professor R.K. Ray.

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